1. Field of the Invention
This invention concerns a water cleaning system comprising at least one reactor device for electrolytic cleaning of polluted water, one flotation device where the pollutants are separated from the clean water, and one device for handling the sludge. The polluted water enters between at least one anode and one cathode across which a voltage is being supplied such that the anode is being continuously sacrificed when an electric current flows through the electrochemical reactor. From the reactor the water flows into the flotation device where the precipitated pollutants flotate as sludge to subsequently be dealt with in the sludge handling device.
2. Prior Art
One problem with reactor designs of the kind described above is that the anode surface, which may be of aluminum, magnesium or another suitable metal or alloy, gets fouled by pollutants and oxidation products during the electrolysis. This lowers capacity and reduces efficiency. Attempts have been made to solve this problem by rotating the anode (EP-31614), by alternating the polarity on the electrodes (DE-4315117/EP-623558), by having very high pressure on the inflowing water (U.S. Pat No. 4,236,990), by a distance piece between anode and cathode for mechanical scraping the anode clean (SE-470423), or by using a high pressurized liquid for flushing of the anode surface (SE-470554).
Another problem is to obtain sufficiently high separation efficiency without high consumption of anode material and energy. This is attempted solved by having a short distance between the electrodes (NO-143147/FI-55166 and SE-470554) or by mounting the anode within a cylindrical shaped cathode and create powerful agitation or rotation of the water to get a centrifugal effect in addition to the electrical field effect (U.S. Pat No. 5352343).
Even though the problem of anode fouling is partly solved by
SE-470554 and the distance between the electrodes is kept relatively short, which lead to a relatively low power consumption, it is not possible at present to combine high separation efficiency and a low consumption of anode material per cubic meter cleaned water. This leads to higher operating costs, than necessary.